I've been lurking about, gleaning information from here, and I've read Chris Scott's book.
I understand that you can cover the costs of a trip by taking and selling the right make and model. Which countries tend to buy at higher prices, or are they all similar? It is obviously easier to sell once in Mauritania, but is it worth pushing on farther south from a strictly monetary perspective?
And, as mentioned by Mr. van der Aa in the book, has the steady improvement of the route had any impact on prices?